1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for subsea drilling.
2. Discussion of the Background
During the past years, with the increase in price of fossil fuels, the interest in developing new production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of fossil fuel.
However, a problem posed by the underwater exploration, and especially deep water exploration, is the control of gas in the marine riser. The marine riser (or a lower marine riser package) is essentially a pipe made of many components that connects a rig or vessel that floats at the surface of the water to a blowout preventer provided undersea at a well head. These elements are shown in FIG. 1. More specifically, an oil and gas exploration system 10 includes a vessel (or rig) 12 having a reel 14 that supplies power/communication cables 16 to a controller 18. The controller 18 is disposed undersea, close to or on the seabed 20. In this respect, it is noted that the elements shown in FIG. 1 are not drawn to scale and no dimensions should be inferred from FIG. 1.
FIG. 1 also shows that a drill string 24 is provided inside a riser system 40, that extends from vessel 12 to one or more BOPs 26 and 28. A wellhead 22 of the subsea well is connected to a casing 44, which is configured to accommodate the drill string 24 that enters the subsea well. At the end of the drill string 24 there is a drill bit (not shown). Various mechanisms, also not shown, are employed to rotate the drill string 24, and implicitly the drill bit, to extend the subsea well. The dirt and debris produced by the drill string 24 are removed by circulating a special fluid, called “mud”, through an inside of the drill string 24 and then through an annulus formed between the outside of the drill string 24 and an inside of the riser system 40. Thus, the mud is pumped from the vessel 12 through the drill string 24 down to the drill bit and back through the annulus of the riser system 40 back to the vessel 12.
The riser system 40 is currently installed in the following way. The vessel 12 stores plural risers that may be connected one to the other to form the riser system 40. Each riser is lowered through a deck of the vessel 12, substantially perpendicular to the surface of the water. Once a first riser is immersed into the water, a second riser is attached to the first riser and further immersed into the water. The process goes on until the first riser reaches the equipment at the well head. At that stage, the first riser is secured to the equipment. Thus, each riser has to have an external diameter less than an internal diameter of a hole in the deck or otherwise the riser cannot be lowered through the deck of vessel 12.
Conventionally, plural pipes are attached to an outside of the riser, e.g., choke line, kill line, blue conduit, yellow conduit, etc. and form a riser assembly. Also, in order to prevent a possible gas bubble to propagate from the well to the vessel, a gas handler may be attached to at least a riser assembly of the riser system 40. Such a riser assembly 50 having a riser 51 with a gas handler 52 is shown in FIG. 2. The riser 51 has a top end 54a and a lower end 54b configured to connect to other risers. FIG. 2 also shows the various lines (pipes) 56a to 56d that run along an outside of the riser 50. Because of the size limitations of the deck of the vessel, FIG. 2 shows that the lines 56a to 56d are bent and provided at a single side 58 of the gas handler 52 in order to reduce an overall exterior diameter of the riser assembly 50 to fit through the deck.
However, from a manufacturing point of view, bending the pipes 56a to 56d as shown in FIG. 2 is time consuming and adds to the overall cost of the riser assembly. Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks.